1. Scope of the Invention
The present invention relates to image processing and more specifically for reducing noise in a sequence of images.
2. Discussion of Prior Art
Imaging, and identification of separate objects is important in various disciplines. Uses may include imaging for medical diagnosis, machine vision, and identification of objects in pictures or videos. To simplify matters, the discussion here will concentrate on medical imaging, however, this may easily apply to other image processing applications.
One specific use for segmentation in medical imaging is for diagnosing coronary artery disease, the leading cause of death in the United States and a major contribution to health care costs. Medical images are acquired and segmented into blood pools and artery surfaces to determine if coronary arteries are blocked, typically leading to major cardiac problems. Despite recent advances in magnetic resonance (MR) cardiac imaging, x-ray catheterization coronary angiography has less noise and is the definitive examination for coronary artery disease. The vessel morphology is examined from different viewpoints using contrast material injected with a catheter into either coronary vessels which are examined with fluoroscopic imaging techniques. If the coronary vessels could be examined and diagnosed with MR imaging, patients with insignificant disease may not have to undergo painful catheterization.
Several methods exist to post process images to determine the boundaries of vessels to diagnose if the vessels are blocked. One such method is a "snake" algorithm as described in "A Geometric Snake Model for Segmentation of Medical Imagery" by A. Yezzi, S. Kichenassamy, A. Kumar, P. Olver, and A. Tannenbaum, IEEE Transactions on Medical Imaging, vol. 16, pp. 199-209, 1997, which tries to approximate curved boundaries by mathematically deforming a curved "snake" to match the boundary. These methods do not work well when the data has a large degree of noise, common in MR cardiac imaging and typically produce inaccurate results.
Currently, there is a need for a system which reduces noise in images with little effect upon detail, such that boundaries of the vessels may be determined.